[Plan] Dashboard 2.1.0 Plan (^11.2 ONLY)

Problem/Motivation

We released 2.0.0 supporting ^10.2 and ^11. Given the importance of the core experimental navigation integration, catching up while not dropping anyone behind has been a $f@?23^HHH challenge. It's time to move on.

This issue serves as a plan, but also as a public announcement. Upgrade your sites asap!

Proposed resolution

• ✅ Release a last compatible version with core ^10.2 || ^11 (done: 2.0.1).
• ✅ #3543062: Restrict Dashboard support only for Drupal ^11.2
• ✅ Fix #3537190: Impossible to save dashboard layout when a block contains a form with a simpler approach, as core Layout Builder takes care of that now.
• ✅ Deal with the navigation icon once and for all (probably at #3509015: Dashboard icon missing from Navigation, but this has been reported in dozens of issues now).🎉
• ✅ #3543075: Remove [LegacyHook] support (aka remove dashboard.module file)
• ✅ #3543079: Convert phpdoc doctrine plugin annotation to modern attributes
• ✅ Release 2.1.0 🎉

Remaining tasks

Check off that list above.

User interface changes

The icon is back.

API changes

Supporting ^11.2 only

Data model changes

None.